Tropheus duboisi Marlier, 1959

Etymology: The species is dedicated to Jean Dubois, a chemist and collaborator of Georges Marlier.

Diagnosis: Tropheus duboisi differs from all others Tropheus by its narrower, rounded, sub-terminal mouth (vs. squarish, down-turned and broad). Differs also by its color patterns: blue head and black body in adults, with a more or less broad white to yellowish band on the chest, and black with rows of white dots in juveniles. 5 spines in anal fin.

Size: Up to 14 cm total length in imports, sometimes more than 15 in aquarium. Females usually slightly smaller than males.

Sex dimorphism: There is no difference in the color pattern between the sexes but males usually grow a little larger than females.

Type locality: Memba, Lake Tanganyika, Congo.

Distribution: A comparatively low number of populations is known. The only congolese population comes from the type locality (Pemba). On the eastern coast, the species is found, from north to south, at Kigoma, Maswa, Cape Kabogo, Halembe, and Karilani Island. The so-called "Maswa" duboisi, which shows the broadest and most yellowish band, comes from the area between Maswa and Halembe.

Localities: Cape Kabogo (Tanzania, undefined), Halembe (Tanzania, native), Hapa Ingii Fara Village (Tanzania, undefined), Karilani Island (Tanzania, native), Kigoma (Tanzania, native), Luagala Point (Tanzania, undefined), Maswa (Tanzania, native), Mkuyu Point (Tanzania, undefined), Pasagulu Point (Tanzania, undefined), Pemba (Congo, Democratic Republic, native).

Habitat: Inhabits rocky shores, where it is usually pushed down by its more evolved congeners of moorii type to deeper layers (up to 30 m, usually more abundant between 6-10 m) and less favorable sediment-rich areas.

Feeding: Feeds from the rock algal bio-cover (aufwuchs) which is torn off the substrate in a less efficient fashion than in other Tropheus, since the mouth is narrower and less down-turned, thus increasing the angle between the body and the substrate.

Breeding: As other members of the genus, Tropheus duboisi is a maternal mouth-brooder which produces a rather low egg number (usually from 6-20). In compensation, the pear-shaped eggs are among the largest in the family (7 mm in the longest diameter), giving birth to rather large and well developed young. The incubation period is basically four weeks, but often continues during several more weeks (up to 10), during which the young are released from time to time by the mother in sheltered areas or may feed inside their mother's mouth. The male does not take any part in the parental care and usually chases the female immediately after spawning, but in the aquarium, may tolerate her in the immediate surrounding of his territory.

Aquaristics: Despite its marked morphological differences and lower population density in the natural habitat, Tropheus duboisi does not differ markedly from its congeners in the aquarium. In the aquarium, males of all Tropheus species tend to defend their own territory, while linear hierarchies are found only in case of overcrowded small tanks. In order to observe their natural behavior in the aquarium, Tropheus must be kept in small groups of several males and females in a large tank (at least 500 l, preferably 1000 l or more) together with other tropheines such as Petrochromis or Simochromis. In smaller tanks, their vicious attacks on subordinates usually lead to the eradication of all smaller males and females, unless the tank is markedly overcrowded. In some cases, when the sexes fit well together, they may be kept as a single pair, a situation which may last several months or years.

The water of the aquarium must be powerfully filtered, hard and alkaline (pH 8.2), with a temperature range around 23-26°C. These fishes must be given mainly ballast-rich foods, as they are very sensitive to intestinal diseases. As for all members of the genus, Tropheus duboisi tend to pick at the fins of its tankmates, especially when young, thus sometimes reducing considerably the fin's extensions to unsightly ruffles.

Conservation: Tropheus duboisi is evaluated by the international union for the conservation of nature in the iucn red list of threatened species as (VU) vulnerable (2006). This restricted range species is rather sensitive to over exploitation for the aquarium trade; the "Maswa" form is reputedly over fished, and is less often available in the imports.

Comments: Considering its narrow sub-terminal mouth, less specialized than in Tropheus moorii types, Tropheus duboisi is probably the most primitive species in the genus. Despite some resemblance in coloration with Tropheus sp. 'black' (black pattern with a broad band on the body), Tropheus duboisi shows a peculiar juvenile color pattern (black with white dots). This color pattern is lost with sexual maturity, while other members of the genus are still able to show juvenile coloration in submissive individuals (especially females).

Tropheus duboisi is also probably the only tropheine with a complete loss of anal ocelli —they are reduced but still visible in other members of the genus.

The width of the vertical band is variable from one individual to another, some of them even show considerable differences from one side to another, while some other individuals lack it completely. Unfortunately, the "Maswa" duboisi from Halembe, which shows the broadest and most yellowish band is victim of its success, though specimens from other locations with pure white bands are worth the value.